1. Field of the Invention
This invention relates to a camera crane, having a moving carriage, a crane post arranged above the truck, and a boom which is attached to the crane post to pivot about a crane pivot axis, where the crane column has sections of the boom which extend on both sides of the crane pivot axis, wherein a camera is attached at an end of one section of the boom, and on the other section a moment-compensating counterweight is attached.
2. Discussion of Related Art
Camera cranes of the type described above are extensively used in motion picture and television productions and allow a suspended movement of movie or video cameras during filming. Camera cranes distinguished between so-called camera dollies, which allow the camera to be lifted only a short distance but which can be moved with a carriage on rails or freely on a support, thus allowing different movements of the camera, and larger camera cranes, which are usually located in a fixed position and have the ability to move the camera by a boom.
A camera crane is known from German Patent Reference DE 38 15 342 C1, but refinements can be made to this crane apparently only insofar as the possible movements of the camera attached to it are concerned. In particular, it is considered a drawback with known camera cranes, that the boom can only travel over a limited pivot range, which results in an undesirable restriction of the camera movements which can be achieved.
It is one object of this invention to provide an improved camera crane of the above mentioned type but which has a significantly increased range of movements of the camera attached to it.
To accomplish the object, one design of the camera crane according to this invention is discussed in the following specification and in the claims.
According to this invention, the object is accomplished with a section of the boom which carries the counterweight having a shorter length than the length of the crane post between the carriage and the crane pivot axis. The boom presents a range of inclination about the crane pivot axis of more than 180xc2x0. Thus, with the possible range of inclination of the boom about the crane pivot axis of more than 180xc2x0, which is achieved as a result of the shorter length of the section of the boom compared to the length of the crane post, a significantly increased ability to move the camera attached to the camera crane is achieved compared to known camera cranes. Thus a significant improvement in the possibilities of framing the picture with the camera crane is achieved according to this invention.
Known camera cranes present an angle of inclination of at most 120xc2x0, namely xc2x160xc2x0 with respect to the horizontal. The camera crane according to this invention, in contrast, allows a much greater inclination of angle, for example, up to 300xc2x0.
Advantageously, the boom has on several parts several telescoping elements, which jointly form the section which is used for the attachment of the camera, so that the length of the section can be changed. Thus, the camera attached to the boom can be raised to a great height by extending the telescoping elements in the vertical arrangement of the boom, or in the case of a horizontal orientation of the boom, it also allows movements over long distances, so that the camera dollies which for these purposes were required in the past can be effectively replaced. Because the change in the length of the boom, which is achieved with the telescoping elements that can be moved in or out, occurs exclusively in the area of the section which is used for the attachment of the camera. The shorter length according to this invention of the other section of the boom compared to the length of the crane post is maintained between the carriage and the crane pivot axis. Thus, independently of the changing length of the section used for the crane attachment, a range of inclination of the boom on the crane pivot axis of more than 180xc2x0 can be maintained.
The moment-compensating counterweight is preferably arranged so that it can be slid on the section of the boom so that, in accordance with the weight of a given attached camera, an adjustment can be made, and it is also possible to adjust the length, which can be changed by the telescoping elements, of the section which is used for the attachment of the camera. In this case, the position of the counterweight is preferably adjusted during the extension of the telescoping elements of the boom, where the adjustment occurs in the opposite direction and is proportional on the section of the boom assigned to it, to compensate for moments.
For the attachment of the camera to the boom, an attachment platform for the camera is provided, which can be pivoted over a horizontal axis as well as over a vertical camera tilt axis, in order to account for the high range of inclination of the boom about the crane pivot axis, which is achieved according to this invention.
It is preferred to have a measuring device to measure the inclination of the boom about the camera tilt axle, for example appropriate displacement sensors. The tilting of the attachment platform about the horizontal axis is continuously readjusted according to the measured inclination of the boom about the camera tilt axis. It is thus possible to ensure a horizontal orientation of the camera within the attachment platform independently of the inclination of the boom. Naturally, other inclinations of the attachment platform can also be permanently maintained besides the horizontal orientation.
In another embodiment of this invention, the crane post is rotatably attached to move about the vertical axis of rotation with respect to the carriage in order to allow corresponding rotation of the camera about the vertical axis of rotation.
To facilitate the transport of the camera crane according to this invention, the boom is preferably attached to the crane post in a removable manner, which can be achieved by attaching the boom to the side of the crane post, as explained in greater detail below.
Other movement possibilities of the camera which is secured to the camera crane according to this invention are possible because the camera itself is held by a pivot head to the attachment platform, whereby the camera can be moved about a horizontal camera tilt axis as well as a camera roll axis which runs in the viewing direction of the camera. While the horizontal axis of the attachment platform is preferably used to ensure the horizontal orientation of the attachment platform independently of the inclination of the boom, the inclination of the pivot head about the camera tilt axis also allows a change in the orientation of the camera about the camera tilt axis, independently of the position of the camera crane.
In one embodiment of the camera crane according to this invention, it is possible for all the movements of the boom, the crane post, the attachment platform and/or the pivot head to be effected by electric motors, and there is a control device for the electric motors. The electric motors themselves can advantageously be designed to be directly driven, where only magnets and corresponding coils are attached to the components which move relative to each other, and adjustment is achieved, which is free of play and has high positioning precision.
The control device of the camera crane according to this invention can advantageously comprise a data storage device to store several positions of the camera crane and a processor, by which the movements of the camera crane between successive positions can be calculated and subsequently automatically carried out. Thus, one or more automated shooting sequences can be carried out by the camera crane according to this invention.
For this purpose, the desired camera positions are manually adjusted, and stored in the data storage of the control device. By corresponding measurement recording devices, the camera position which was achieved in the process is unequivocally recorded, because the rotation of the crane post about the vertical axis of rotation, the inclination of the boom about the crane tilt axis, the position of the telescoping elements of the boom, the inclination of the pivot head about the camera tilt axis as well as about the camera roll axis, and the rotation of the attachment platform about the vertical camera tilt axis are precisely measured in degrees and stored. With a known calculation function, for example, the spline function, the processor then calculates the movement paths of the camera crane which are required between two such positions stored in the data storage device, about the given axes, so that subsequently an automatic passage through this path between the individual stored positions is possible, and can be carried out with extremely high precision of reproduction.
To control the desired positions during the manual movement, it is possible, for example, to provide a control console which is positioned at a distance from the camera crane, and is equipped with monitors and elements for controlling the different drive instructions to the camera crane.